Scientists in Japan have used human blood to successfully create immature human egg cells in a lab for the first time, according to new research published Thursday in Science. The work is a major breakthrough in stem cell research and may lead the way to babies that can be created in a lab using the body tissues or blood of their relatives.

Mitinori Saitou, a biologist at Kyoto University who contributed to this pioneering research, managed to produce mouse eggs and sperm from stem cells back in 2012and used them to breed healthy baby mice. It was the first time that eggs were created from embryonic stem cells.

When Saitou and his colleagues first produced artificial mouse egg cells, these were grown to maturity inside a simulated mouse ovary constructed from the tissue of fetal mice. Since this tissue would be next to impossible to obtain from humans, the researchers had to figure out a different way of creating an artificial ovary.